This invention relates to a photoelectron microscope such as an X-ray microscope or the like wherein a specimen is irradiated with X rays, or ultraviolet or synchrotron radiation, so that the specimen or a photocathode disposed in close proximity of the specimen emits photoelectrons by means of which an image of the specimen is formed.
The X-ray microscope of the type with which the invention is concerned uses an X-ray source such as a conventional X-ray tube which continuously emits X rays, and a focusing coil for forming an enlarged photoelectron image of the specimen.
With a continuous radiation source it is impossible to make a real-time measurement or obtain images of high resolution.
The photoelectrons emitted by the specimen irradiated with X rays or a photocathode disposed in contact therewith have different energy levels, and in order to obtain photoelectron images at different energy levels, a meshed energy filter is arranged adjacent to the image plane of the enlarged photoelectron image, with resulting complication of the structure of the microsope and reduction of the transmittance of photoelectrons and consequent darkening of the images obtained.
With a focusing coil for forming an enlarged photoelectron image of a specimen it is difficult to obtain a good image due to an astigmatic aberration caused by different energy levels of the photoelectrons and a spherical aberration caused by different emission angles thereof. To reduce the aberrations it is necessary to use an aperture stop or a correction lens, with resulting reduction in the efficiency of using the photoelectrons and darkening of the image obtained.
To avoid such undesirable results, it has been proposed to use a superconductive coil to obtain a strong divergent magnetic field in which the emitted photoelectrons advance along the flux lines to form an enlarged image of the object under observation (cf. Nature, Vol. 290, Apr. 16, 1981, pp 556.about.559). To make a superconductive coil operate, however, liquid helium and equipment therefor are required, so that the whole apparatus becomes complicated and large in size and cannot be made readily available for general use.
Accordingly, it is one object of the invention to provide a photoelectron microscope such as an X-ray microscope or the like which employs a radiation source so designed as to produce radiation pulses within a predetermined short wavelength range including X rays and ultraviolet rays to irradiate a specimen to be analyzed, and a normal conductive coil for producing a divergent magnetic field, with means for energizing the coil in synchronism with the radiation pulses.
Another object of the invention is to provide such a photoelectron microscope as mentioned above which uses neither a superconductive coil for producing a divergent magnetic field nor a meshed energy filter in order to obtain photoelectron images of different energy levels.